Process for the synthesis and recovery of nitramines

ABSTRACT

A method is provided for the synthesis of nitramines and the recovery of the nitramines from a clathrate.

RELATED APPLICATION

[0001] This application is a divisional of application Ser. No.10/060,051, filed Jan. 29, 2002, pending, which claims the benefit ofpriority of U.S. provisional application No. 60/266,030 filed in theU.S. Patent & Trademark Office on Feb. 1, 2001, the complete disclosureof which is incorporated herein by reference.

GOVERNMENT LICENSING RIGHTS

[0002] The U.S. Government has a paid-up license in this invention andthe right in limited circumstances to require the patent owner tolicense others on reasonable terms as provided for by the terms ofcontract F04611-99-C-0010 awarded by the Air Force Research Lab.

BACKGROUND OF THE INVENTION

[0003] 1. Field of the Invention

[0004] This invention generally relates to the synthesis and recovery ofenergetic materials, especially for use in gun and rocket propellantsand explosives. More specifically, the invention relates to thesynthesis and recovery of nitramines.

[0005] 2. State of the Art

[0006] Nitramines are highly energetic compounds having found wideacceptance in the art of explosives and rocket propellant. The mostcommon nitramines in use in the explosives and propellant arts today are1,3,5-trinitro-1,3,5-triaza-cyclohexane (RDX) and1,3,5,7-tetranitro-1,3,5,7-tetraaza-cyclooctane (HMX). The acceptance ofRDX and HMX in the art is generally attributed to the high energeticperformance and the high energy density possessed by these compounds. Inessence, RDX and HMX are the standards of energetic performance andenergy density by which other energetic compounds are measured.

[0007] A drawback to RDX and HMX is that these nitramine compounds arerelatively sensitive to shock, friction, and impact. The highsensitivities associated with RDX and HMX make these nitramine compoundsless desirable for some applications, especially where the compounds areused or stored in an environment in which traumatic stresses may beencountered. By way of example, in a military conflict, the traumaticimpact of hostile ammunition into a rocket motor or weaponry carryingRDX or HMX can lead to destruction of surrounding objects and loss ofhuman life. In the event that the impacted rocket motor or weaponry isin proximity to arsenal or other explosive or combustible materials,catastrophic damage may result.

[0008] There is thus a need in the art to provide a highly energetic andhigh energy density compound that is relatively insensitive to physicalstimuli, such as shock, impact, and friction. Various other nitraminecompounds have been synthesized towards this end. For example, U.S. Pat.No. 4,085,123 to Flanagan et al. describes the synthesis of thenitramine compound 1,3-diazido-2-nitrazapropane (DANP) as an energeticliquid plasticizer for solid propellants. According to Flanagan et al.,the DANP azide plasticizer is synthesized by generating a solution of1,3-diacetoxy-2-nitrazapropane and dioxane and saturating the solutionwith anhydrous chloride gas. The use of anhydrous chloride gas makesthis process extremely hazardous. In this regard, the Flanagan et al.patent states that the resulting DANP plasticizer is sensitive and mustbe handled with caution. Moreover, the acetate and chloride precursorsare inherently impure, since their reactions reach and remain atequilibrium. In order to minimize the impurities, Flanagan et al. teachdistilling both the 1,3-diacetoxy-2-nitrazapropane precursor and itschlorine analogue prior performing the reactions. On an industrialscale, these distillation techniques are impractical and highlyhazardous.

[0009] Another nitramine synthesis route is disclosed in U.S. Pat. No.5,243,075 to Cason-Smith, which describes contacting an N-acetoxymethylnitramine with a mixture of concentrated hydrochloric acid andtrifluoroacetic acid to produce the corresponding N-chloromethylnitramine analogue. The chlorinated nitramines produced by this processare not sufficiently robust or chemically stable for effective use as anenergetic material. The chlorine atoms of the N-chloromethyl nitraminesare inherently unstable. When heated, hydrogen chloride gas is released.The presence of the HCl acid can lead to degradation of the material viaautocatalysis.

[0010] The synthesis of1,3-bis-(3′5′-dinitro-1′,2′,4′-triazolo)-2-nitrazapentane (BNTN is alsoknown. BNTN has the following structure:

[0011] Specifically, it is known to produce BNTN by suspending sodiumdinitro-1,2,4-triazole in dry acetonitrile, and adding2-nitraza-1,3-dichloropropane. It is believed by the inventors that the2-nitraza-1,3-dichloropropane is prepared by reacting2-nitraza-1,3-diacetoxypropane with an inorganic chlorinating agent,such as phosphorus pentachloride (PCl₅). According to this method,however, the 2-nitraza-1,3-diacetoxypropane must be purified bydistillation prior to chlorination to avoid the formation of chlorineby-products. Another distillation step is needed prior to the reactionof the 2-nitraza-1,3-dichloropropane with the sodium salt ofdinitro-1,2,4-triazole. The hazardous nature and toxicity of2-nitrazapropane and its by-products make distillation highlyundesirable and impractical to produce on an industrial scale. Further,the 2-nitraza-1,3,-dichloropropane is very electrophilic and may reactwith incidental moisture to replace the chlorine atoms and formhydroxymethyl nitramines, thus complicating the nucleophilic addition ofthe triazole.

[0012] The inventors have found that the technique disclosed in theCason-Smith patent is not suitable for making BNTN. The conditions setforth in the Cason-Smith patent—e.g., treating with HCl andtrifluoroacetic acid—were insufficient to drive the reaction of2-nitraza-1,3-diacetoxypropane and, as a consequence, a largely impureproduct was obtained.

BRIEF SUMMARY OF THE INVENTION

[0013] This invention provides a synthesis route for preparing andrecovering nitramine compounds having one or more N-heterocyclomethylgroups. The nitramine compounds preferably possess relatively highenergetic performance, comparable or superior energy density, andrelatively low sensitivity to physical stimuli (e.g., shock, friction,and impact) in relation to the current standards of RDX and HMX.

[0014] This invention also provides a method by which anN-heterocyclomethyl polynitrazaalkane can be precipitated at high yieldsfrom a solvent that forms a clathrate with the N-heterocyclomethylpolynitrazaalkane.

[0015] This invention further provides a method for synthesizing atriazole, such as 3,5-dinitro-1,2,4-triazole.

[0016] This invention still further provides a method for synthesizing asalt of a triazole, especially dinitrotriazole.

[0017] It is to be noted that, as used in the specification and theappended claims, the singular forms “a,” “an,” and “the” include pluralreferents unless the context clearly dictates otherwise. Thus, by way ofexample, the term “polynitrazaalkane” includes in its definition notonly a single polynitrazaalkane, but also a combination of two or morepolynitrazaalkanes.

[0018] The term “polynitrazaalkane” means a nitrazaalkane having two ormore nitraza (nitramine) groups. A nitraza group may be internallypositioned along the azaalkane chain, or can be at a terminal position.

[0019] In accordance with an aspect of this invention, N-acetoxymethylnitrazaalkane having an azaalkane chain (or backbone) of at least fiveatoms is halogenated to form an N-halomethyl nitrazaalkane. TheN-halomethyl nitrazaalkane comprises at least one halomethyl moietyhaving a halogen atom, with the halogen atom comprising chlorine,bromine, or iodine. A salt of a heterocyclic nucleophile is reacted withthe N-halomethyl nitrazaalkane to form an N-heterocyclomethylnitrazaalkane. The solvent in which the nucleophilic substitution takesplace forms a clathrate with the N-heterocyclomethyl nitrazaalkane. Inaccordance with the teachings of this invention, the N-heterocyclomethylnitrazaalkane may be precipitated in a nonsolvent and recovered from thenonsolvent.

[0020] In accordance with another aspect of this invention, a method isprovided for N-heterocyclomethylating a terminal nitraza moiety orterminal nitraza moieties of a polynitrazaalkane. In accordance with theteachings of this invention, the N-heterocyclomethyl polynitrazaalkanemay be precipitated in a nonsolvent and recovered.

[0021] In accordance with still another aspect of this invention, amethod is provided for preparing 3,5-dinitro-1,2,4-triazole or a saltthereof. The method comprises nitrating 3,5-diamino-1,2,4-triazole in anacidic solution having a pH not greater than about 3 to form3,5-dinitro-1,2,4-triazole. The 3,5-dinitro-1,2,4-triazole is extractedfrom the acidic solution with little or no neutralization, so that thepH of the acidic solution during extraction is no greater than about 3.Optionally, the 3,5-dinitro-1,2,4-triazole may then be treated with abase to form a 3,5-dinitro-1,2,4-triazole salt.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0022] The accompanying drawings are incorporated in and constitute apart of the specification. The drawings, together with the generaldescription given above and the detailed description of the preferredembodiments and methods given below, serve to explain the principles ofthe invention. In such drawings:

[0023]FIG. 1 is a flow chart setting forth a procedure for preparing1,7-bis-(3′,5′-dinitro-1′,2′,4′-triazolo)-2,4,6-trinitrazaheptane inaccordance with an embodiment of this invention;

[0024]FIG. 2 is a flow chart setting forth a procedure similar to thatof FIG. 1, but used to prepare1,5-bis-(3′,5′-dinitro-1′,2′,4′-triazolo)-2,4-dinitrazapentane;

[0025]FIG. 3 is a flow chart setting forth a procedure for preparing1,9-bis-(3′,5′-dinitro-1′,2′,4′-triazolo)-2,5,8-trinitrazanonane inaccordance with another embodiment of this invention;

[0026]FIG. 4 is a flow chart setting forth a procedure for preparing1,9-bis-(3′,5′-dinitro-1′,2′,4′-triazolo)-2,5,8-trinitrazanonane inaccordance with still another embodiment of this invention;

[0027]FIG. 5 is a flow chart setting forth a procedure for preparing1,9-bis-(3′,5′-dinitro-1′,2′,4′-triazolo)-2,5,8-trinitrazanonane inaccordance with a further embodiment of this invention;

[0028]FIG. 6 is a flow chart setting forth a procedure for preparing1,9-bis-(3′,5′-dinitro-1′,2′,4′-triazolo)-2,5,8-trinitrazanonane inaccordance with still a further embodiment of this invention;

[0029]FIG. 7 is a flow chart similar to FIG. 3, setting forth aprocedure for preparing1,6-bis-(3′,5′-dinitro-1′,2′,4′-triazolo)-2,5-dinitrahexane;

[0030]FIG. 8 is a flow chart similar to FIG. 4, setting forth aprocedure for preparing1,6-bis-(3′,5′-dinitro-1′,2′,4′-triazolo)-2,5-dinitrahexane;

[0031]FIG. 9 is a flow chart setting forth a procedure for preparing1,6-bis-(3′,5′-dinitro-1′,2′,4′-triazolo)-2,5-dinitrahexane inaccordance with another embodiment of the invention;

[0032]FIG. 10 is a flow chart similar to FIG. 5, setting forth aprocedure for preparing1,6-bis-(3′,5′-dinitro-1′,2′,4′-triazolo)-2,5-dinitrahexane;

[0033]FIG. 11 is a flow chart similar to FIG. 6, setting forth aprocedure for preparing1,6-bis-(3′,5′-dinitro-1′,2′,4′-triazolo)-2,5-dinitrahexane; and

[0034]FIG. 12 is a flow chart setting forth a procedure for preparing1,6-bis-(3′,5′-dinitro-1′,2′,4′-triazolo)-2,5-dinitrahexane according tostill another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0035] Reference will now be made in detail to the presently preferredembodiments and methods of the invention as described below. It shouldbe noted, however, that the invention in its broader aspects is notlimited to the specific details, representative devices and methods, andexamples described in this section in connection with the preferredembodiments and methods. The invention according to its various aspectsis particularly pointed out and distinctly claimed in the attachedclaims read in view of this specification, and appropriate equivalents.

[0036] A method of preparing an N-heterocyclomethyl nitrazaalkane inaccordance with one preferred embodiment of the invention is generallyshown in FIGS. 1 and 2. Referring more particularly to FIG. 1, there isshown a method of making1,7-bis-(3′,5′-dinitro-1′,2′,4′-triazolo)-2,4,6-trinitrazaheptane(BNTH). An N-diacetoxymethyl nitrazaalkane precursor is first preparedin any manner known in the art. The synthesis of thisprecursor—1,7-diacetoxy-2,4,6-trinitrazaheptane—may be performed byreacting diacetate, hexamine, and nitric acid. The synthesis of1,7-diacetoxy-2,4,6-trinitrazaheptane is described in U.S. Pat. No.5,243,075, the disclosure of which is incorporated herein by reference.The N-diacetoxymethyl nitrazaalkane is halogenated to replace theacetoxy moieties with a halogen atom, such as chlorine, bromine, oriodine. The halogenation may comprise chlorinating with, for example, amixture comprising concentrated hydrochloric acid and trifluoroaceticacid, or a combination of phosphorus pentachloride in a solvent. Thehalogenation is preferably conducted in a solvent comprising at leastone member selected from the group consisting of methylene chloride,chloroform, and dioxane. The resulting dichloride nitramine mayoptionally be recrystallized prior to further processing.

[0037] Next, the 1,7-dichloro-2,4,6-trinitrazaheptane is subject to anucleophilic replacement with a salt of a substituted heterocycle group.The heterocyclic ring may be aromatic or nonaromatic, although aromaticrings are currently preferred. Examples of heterocycles that may be usedin this embodiment and the other embodiments described in the summaryabove and this detailed description include five and six member ringscontaining at least one endocyclic heteroatom. Representative 5-memberedand 6-membered heterocyclic rings include triazoles, imidazoles,pyrazoles, oxazoles, isoxazoles, and tetrazoles. This list is notintended to be exhaustive. Additionally, three and four memberheterocycle rings that may be used include, for example, aziridines andazetidines. The heterocylic groups may be substituted with one or moreexocyclic ring substituents, such as, by way of example, nitro groups,azido groups, and amino groups. Nitro substituents are preferred.Preferred nucleophiles include mononitrotriazole, dinitrotriazole,mononitroimidazole, dinitroimidazole, and trinitroimidazole.

[0038] The nucleophile is typically introduced into the reaction as asalt. Suitable cations for the nucleophile include potassium, sodium,lithium, and tetraalkyl ammonium (alkyls are the same or different andare each preferably 1 to 4 carbon atoms).

[0039] The reaction of potassium 3,5-dinitrotriazolate with thechloromethyl-nitramine electrophiles is greatly facilitated by theinclusion of two equivalents of sodium bromide in the reaction. Ineffect, this salt mediates an in-situ trans-halogenation. The reactionis much cleaner, because the reaction proceeds more quickly. When thereaction is complete, the sodium chloride and potassium bromide areremoved by filtration. The organic solvent, THF, is then removed invacuum and the residue partitioned between water and ethyl acetate. Twoor three water washes serve to remove all of the starting materials andbyproducts. After drying and removal of the ethyl acetate, the residueis recrystallized from THF/MTBE.

[0040] The nucleophilic replacement takes place in one or more solvents.Representative solvents for this reaction include one or more membersselected from the group consisting of acetonitrile, dioxane, lowmolecular weight alcohols (e.g., methanol, ethanol, and propanol), andtetrahydrofuran.

[0041] The inventors have found that the heterocyclonitramines producedby this and other processes described in this detailed description areextremely difficult to isolate as pure solids from the solvents. Onepartially successful approach was to precipitate the entire reactionmixture, including THF, unreacted KDNT, KBr, NaCl, and byproducts,directly into water. Although the THF remained occluded, the othermaterials were successfully removed.

[0042] While not wishing to be bound by any theory, it is believed thatthe reason for this difficulty is solvent occlusion, generally thoughtto be in the form of a clathrate. A clathrate is generally understood inthe art to mean an inclusion complex, such as in the case whereinmolecules of one substance contain an open structure, such as cavities,holes, or channels, typically in a crystalline structure, in which atomsor molecules of another substance are trapped or held.

[0043] The inventors have found that the N-heterocyclomethylnitrazaalkanes produced by this and other embodiments of the inventioncan be recovered from the clathrates by precipitation. Generally, thesolvent-occluded heterocyclomethyl nitramine is fully dissolved in itssolvent so that no (or substantially no) solid nitramine remains. Thesolution is then precipitated into a nonsolvent at such a rate thatcrystals form rapidly, permitting only incidental amounts of solvent tobe included in the crystal structure. Preferably, precipitation isperformed by adding the nitramine-containing solution to the nonsolventslowly, more preferably dropwise. The volumetric ratio of nonsolvent tonitramine-containing solution is preferably at least 2:1, preferably atleast 3:1. Surprisingly, methanol has been found to be a particularlyfavorable nonsolvent for the precipitation of BNTH and other nitraminesproduced within the scope of this invention. Methylene chloride is alsoa suitable nonsolvent for the precipitation.

[0044]FIG. 2 illustrates a method of making1,5-bis-(3′,5′-dinitro-1′,2′,4′-triazolo)-2,4-dinitrazapentane (BNDP) ina manner similar to that of FIG. 1. Synthesis of the1,5-diacetoxy-2,4-dinitrazapentane is also known in the art and can beperformed without undue experimentation, especially in view of U.S. Pat.No. 5,243,075 to Cason-Smith.

[0045] The nitramines illustrated in FIGS. 1 and 2 contain methylenespacers between the nitraza (nitramine) moieties of the azaalkane.Another representative higher homologue having three methylene spacersis1,9-bis-(3′,5′-dinitro-1′,2′,4′-triazolo)-2,4,6,8-tetranitrazapentane.It is to be understood that dimethylene (i.e., ethylene) or othermulti-methylene spacers may be present in the azaalkane chain (inaddition to or as an alternative for the methylene spacers). Theazaalkane chain may also be branched, with the branches optionallycontaining nitraza moieties and/or a terminal cite for nucleophilicsubstitution of a heterocyclic moiety. It is also possible to make aheterocyclomethyl nitrazaalkane having only a single heterocyclicmoiety, such as by starting with a mono-acetoxy-nitrazaalkane, such asone selected from the group consisting of1-acetoxy-2,4,6-trinitrazaheptane, 1-acetoxy-2,4-dinitrazapentane, and1-acetoxy-2,4,6,8-tetranitrazanonane. Another possibility is for one ormore of the terminal moieties to be substituted with an energeticfunctionality other than a heterocylomethyl group, for example, an azidogroup, so long as at least one heterocyclomethyl group is present in themolecule.

[0046] FIGS. 3-12 illustrate a representative, but not exhaustive, setof exemplary synthesis routes for preparing heterocyclomethylpolynitramines. Each of these synthesis routes comprises the recovery ofthe N-heterocyclomethyl polynitrazaalkane from a clathrate byprecipitation in a nonsolvent.

[0047] As illustrated in FIGS. 3, 4, and 7-9, the polynitrazaalkanes maybe heterocyclomethylated by halomethylating the polynitrazaalkane with,for example, paraformaldehyde and a halogenating agent to form anN-halomethyl polynitrazaalkane. In the illustrated examples, thehalogenating agent may be selected from the group of hydrogen chloride,phosphorus pentachloride, sulfurial chloride, and thionyl chloride, withhydrogen chloride being preferred. The halomethylating may be performedat room temperature or lower. Depending upon the selected halogenatingagent, volatiles may be evaporated, and the product recrystallized froma suitable solvent. The heterocyclic nucleophile replaces the halogenatom of the N-halomethyl polynitrazaalkane to form theN-heterocyclomethyl polynitrazaalkane. Suitable solvents includeacetonitrile, tetrahydrofuran, dimethylformamide, dimethyl sulfoxide,N-methylpyrrolidone, diethyl ether, or mixtures thereof.

[0048] Another embodiment for heterocyclomethylating thepolynitrazaalkane is illustrated in FIGS. 5, 6, and 10-12. According tothis embodiment, the terminal nitraza moiety of the polynitrazaalkane ishydroxymethylated to form at least one N-hydroxymethyl nitraza moiety.This reaction may occur in water, optionally with a cosolvent such asacetonitrile, tetrahydrofuran, dimethylformamide, dimethyl sulfoxide,N-methylpyrrolidone, or mixtures thereof. The next step involvesesterifying the N-hydroxymethyl nitraza moiety of the polynitrazaalkanewith a leaving group. Suitable leaving groups include: benzenesulfonates and benzene sulfonates substituted with alkyl(s) and/orhalogen atom(s), such as tosylate and brosylate; alkane sulfonates, suchas methane sulfonate; and halogen-substituted alkane sulfonates, such astrifluoromethane sulfonate. The heterocyclic nucleophile is thensubstituted for the leaving group of the polynitrazaalkane to form anN-heterocyclomethyl polynitrazaalkane. Generally, chlorinatedhydrocarbon solvents such as, for example: chloroform, methylenechloride, 1,2-dichloroethane; and polar organic solvents includingtetrahydrofuran and dioxane and the like may be used. Pyridine andsubstituted pyridines may be used as a proton scavenger in thisreaction.

[0049] Representative heterocycles that may be used in the embodimentsillustrated in FIGS. 3-12 include five and six member rings containingat least one endocyclic heteroatom, especially triazoles, imidazoles,pyrazoles, oxazoles, isoxazoles, and tetrazoles. Additionally, three andfour member heterocycle rings that may be used include aziridines andazetidines. The heterocylic groups may be substituted with one or moreexocyclic ring substituents, such as nitro groups, azido groups, andamino groups. Preferred nucleophiles include mononitrotriazole,dinitrotriazole, mononitroimidazole, dinitroimidazole, andtrinitroimidazole. The heterocylic nucleophile is reacted in a suitablesolvent, such as, for example, acetonitrile, dioxane, low molecularweight alcohols (e.g., methanol, ethanol, and propanol), andtetrahydrofuran, dimethylformamide, dimethyl sulfoxide,N-methylpyrrolidone, diethyl ether, or mixtures thereof.

[0050] FIGS. 3-6 illustrate the synthesis of1,9-bis-(3′,5′-dinitro-1′,2′,4′-triazolo)-2,5,8-trinitrazanonane(BNTNN), and FIGS. 7-12 illustrate the synthesis of1,6-bis-(3′,5′-dinitro-1′,2′,4′-triazolo)-2,5-dinitrahexane (BNDNH).Both of these nitramine compounds contain ethylene spacers between thenitraza moieties of the azaalkane chain. It has been found by theinventors that the incorporation of ethylene spacers in the chainunexpectedly produces superior sensitivity properties in thepolynitramine. Although not illustrated, it is possible to producehigher homologues of these ethylene spaced polynitramines, as well aspolynitramines with methylene spacers or spacers longer than ethylenespacers. The azaalkane chain may also be branched, with the branchesoptionally containing nitraza moieties and/or a terminal cite fornucleophilic substitution of a heterocyclic moiety. It is also withinthe scope of the invention to make a heterocyclomethyl nitrazaalkanehaving only a single heterocyclomethyl moiety. Another possibility isfor one or more of the terminal moieties to be substituted with anenergetic functionality other than a heterocylomethyl group, forexample, an azido group, so long as at least one heterocyclomethyl groupis present in the nitramine molecule.

[0051] FIGS. 3-12 illustrate three processes for making polynitraminessuitable for use in this invention.

[0052] The first process for preparing a polynitramine is illustrated inFIGS. 3, 5, 7, and 10, in which a polyamine is perchlorinated to convertthe primary amine moiety or each of the primary amine moieties into arespective N-perchlorinated amine moiety having two chlorine atoms. Anysecondary amine moiety is converted into an N-chlorinated amine moietyhaving one chlorine atom. The perchlorinated polyamine is then nitratedto substitute respective nitro moieties for one of the chlorine atoms ofthe N-perchlorinated amine moiety and for the chlorine atom of theN-chlorinated amine moiety. The polyamine is then dechlorinated toprovide the polynitrazaalkane.

[0053] Suitable perchlorinating agents include, by way of example,sodium hypochlorite, N-chlorosuccinimide, calcium hydrochlorite,CHLORAMINE-T, or other N-chlorosulfonamides. The perchlorination may beperformed in one or more solvents, especially water and/or a polarorganic solvent. The perchlorination is preferably performed at roomtemperature or lower and may be followed by precipitation of theperchlorinated polyamine and filtering of the solvent. The nitrationstep may be performed with nitric acid, such as nitric acid having aconcentration of 70 weight percent or higher, preferably 90 weightpercent or higher. The nitration step may also be conducted at roomtemperature and may be followed by a precipitation and filtering.Dechlorination of the nitrated polyamine may be performed with an alkalimetal hydroxide, such as sodium hydroxide, and is preferably followed bya pH adjustment to a range of 4 to 7 and additional filtering.

[0054] The second process for preparing a polynitramine is illustratedin FIGS. 4, 6, 8, and 11, in which a polyamine comprises at least oneprimary amine moiety and optionally at least one secondary amine moiety.According to this process, the polyamine is acylated under conditions toconvert the primary amine moiety into a monoacylated amine moiety whileleaving the secondary amine moiety nonacylated. The N-acylated polyamineis then nitrated to form one nitro group on each of the primary aminemoieties and another nitro group on the secondary amine moiety. Theprimary moiety is then deacylated to provide the polynitrazaalkane.

[0055] The acylation step may be performed with acetic anhydride orother acyl anhydrides, as well as acid chlorides. The acyl group isrepresented by —C(O)R, wherein R may be, for example, hydrogen, an alkylhaving 1 to 8 carbon atoms, or branched alkyls. Nitration may be formedwith nitric acid, nitronium ion salts, mixed acids (sulfuric and nitricacids), acetic nitric anhydride, and a combination of trifluoroaceticanhydride and a nitrate source (e.g., ammonium nitrate). Deacylation maybe accomplished by hydrolysis in water, or with caustic. These steps aredescribed in George F. Wright, Part 1 of Chemistry of the Nitro andNitroso Groups, pp. 614-680 (1969).

[0056] The third process for preparing a polynitramine is illustrated inFIGS. 9 and 12, in which imidazolidinone (or ethylene urea) is used toprepare 1,2-dinitrazaethylene. This may be carried out at roomtemperature or lower. The imidazolidinone is treated with the nitratingagent or mixture, which may be nitric acid, a mixed acid (sulfuric andnitric acids), and acetic nitric anhydride. Next, the reaction isquenched in a water bath over ice to precipitate the nitroacyl amine,which is then refluxed in water.

[0057] Exemplary nitramines made by this invention were found to possessthe following properties: BNTH BNDP BNTNN BNDNH Formula C₈H₈N₁₆O₁₄C₇H₆N₁₄O₁₂ C₁₀H₁₂N₁₆O₁₄ C₈H₈N₁₄O₁₂ density 1.80 1.845 1.773 1.8205(g/cc) (measured) ΔH_(f)kcal/mol +117 +149.8 +108.0 +143.74 (calculated)(measured) ABL impact 3.5 6.9 6.9 3.5 (cm) ABL friction 800 @ 8 800 @ 8420 @ 8 800 @8 (lbs @ fps) TC ESD 0.25 >8 2.09 0.15 confined TC ESD 8 Nobulk 1 No bulk 8 mass ignition 1 No bulk unconfined ignition ignitionignition (J) TC impact 40 34.78 25.0 40.09 (in.) TCfriction >64 >64 >64 >64 (lbs) SBAT 225 280 225 225

[0058] Density was measured by a gas pycnometer.

[0059] The computational method for calculating heats of formation isdescribed in George A. Olah and D. R. Squire, Chemistry of EnergeticMaterials, Chapt. 4, pp. 77-94 (Academic Press 1991), which isincorporated herein by reference for its teaching of this method.

[0060] The remaining properties were calculated or measured inaccordance with R. B. Cragun, Hazards Properties of a MagnesiumNeutralized Propellant, AIAA Paper No. AIAA-91-2860, which isincorporated herein by reference for its teaching of how to measure orcalculate these properties.

[0061] Dinitrotriazole may be synthesized by nitrating3,5-diamino-1,2,4-triazole in an acidic solution to form3,5-dinitro-1,2,4-triazole. Nitrating may be performed with an alkalimetal nitrite, such as sodium nitrite or potassium nitrite. The acidsolution may comprise hydrochloric acid and/or sulfuric acid.3,5-diamino-1,2,4-triazole may be obtained commercially or prepared inaccordance with the teachings below. The dinitrotriazole is thenextracted from the acidic solution. Suitable solvents for the extractioninclude methyl tert-butyl ether and a dialkyl ether (e.g., diethylether), and mixtures thereof. The acid solution is preferably maintainedat a pH of not more than about 3 or less, preferably not more than about2, and more preferably 1 to 2 during the nitration and extraction. If asalt is desired, the dinitrotriazole may be reacted with a suitable baseat, for example, room temperature or lower. Representative bases includepotassium carbonate, potassium bicarbonate, sodium bicarbonate, andsodium carbonate.

[0062] The family of DNT-disubstituted methylene nitramines have allbeen found to produce solvated crystals.

[0063] The following examples are offered to further illustrate thesynthesis methods of the present invention. These examples are intendedto be exemplary and should not be considered exhaustive of the scope ofthis invention.

EXAMPLES Example 1 Preparation of1,7-bis-(3′,5′-dinitro-1′,2′,4′-triazolo)-2,4,6-trinitrazaheptane

[0064] Step 1. Preparation of 1,7-diacetoxy-2,4,6-trinitrazaheptane

[0065] In a 1 L, 3-neck round bottom flask equipped with a thermometerand condenser set at 15° C., 90 ml of 98% nitric acid and 240 ml ofacetic anhydride were placed. Then, 67.2 grams of hexamine weredissolved in 110 ml of glacial acetic acid and added to the reactionflask via addition funnel, keeping the temperature at 15° C. to 20° C.The reaction was heated to 75° C. then allowed to cool to roomtemperature while stirring. After standing at room temperature fortwelve hours, the solid was filtered and washed with acetic acid.Recrystallization from hot acetic acid yielded 88.42 grams of1,7-diacetoxy-2,4,6-trinitrazaheptane.

[0066] Step 2. Preparation of 1,7-dichloro-2,4,6-trinitrazaheptane

[0067] In a 2 L 3-neck round bottom flask equipped with a thermometerand cooled to 5° C. were placed 783 grams of trifluoroacetic acid and184 grams of concentrated HCl. To this solution, 88 grams of1,7-diacetoxy-2,4,6-trinitrazaheptane were added. The reaction wasstirred for overnight while allowing the reaction mixture to warm toroom temperature. The product was filtered, washed with water and driedunder vacuum to yield 64.42 grams of1,7-dichloro-2,4,6-trinitrazaheptane.

[0068] Step 3. Preparation of1,7-bis-(3′,5′-dinitro-1′,2′,4′-triazolo)-2,4,6-trinitrazaheptane

[0069] In a 1 L 3-neck flask equipped with a thermometer, condenser withdrying tube, and argon purge were added 400 ml of acetonitrile and 7.0grams of 1,7-dichloro-2,4,6-trinitrazaheptane. The mixture was stirredat room temperature until all solids dissolved. To this solution wereadded 9.7 grams of potassium dinitrotriazole and 4.7 grams of sodiumbromide and the solution was stirred at room temperature until allsolids dissolved. The reaction was heated to reflux overnight. Thereaction was cooled to room temperature and solids removed byfiltration. The solution was slowly dropped into water to precipitate avery flocculent solid, which was collected by filtration and dried undervacuum overnight at 45° C. to yield 12.2 grams of product in the form ofa clathrate.

Example 2 Preparation of1,9-bis-(3′,5′-dinitro-1′,2′,4′-triazolo)-2,5,8-trinitrazanonane (BNTNN)

[0070] Step 1. Preparation of diethylene trinitramine

[0071] In a 5 L jacketed reactor cooled to 10° C. to 15° C. were placed3 L of commercial chlorox with a titer of 4% NaOCl content. In a beaker25.8 grams of diethylene triamine were dissolved in 100 ml of waterfollowed by the careful addition of 45 ml of 12M HCl. The diethylenetrinitramine solution thus prepared was then added to the reactor duringthe course of 5-10 minutes with vigorous stirring. The reaction was thenextracted with chloroform 2 times with 50 ml solvent. The organic phaseswere combined and dried over sodium sulfate. To the chloroform solution,51 ml of 98% nitric acid were added while keeping the temperature below10° C. The reaction mixture was then stirred at 10° C. for ½ hour andsubsequently warmed to 35° C. To the warmed nitrating mixture, 200 mlacetic anhydride were added drop-wise over 1 hour. Stirring wascontinued for ½ hour at 30° C. to 35° C. The chloroform was thenevaporated in a stream of dry nitrogen gas during which the productcrystallized. The solid was collected by filtration. The chloronitraminewas next suspended in 1 L water and the pH adjusted to 12 with 50 ml 25%sodium hydroxide solution while monitoring with a pH meter. A thick oilremained that did not dissolve. Decantation away from the insoluble oilresulted in a cloudy caustic solution that was readjusted to pH 5.07whereupon the product precipitated. The precipitant was collected,washed with water then dried under vacuum at ambient temperature. Theyield was approximately 45% of theoretical.

[0072] Step 2. Preparation of 1,9-dichloro-2,5,8-trinitrazanonane

[0073] In a 5 L jacketed 3-neck reactor equipped with a top stirrer andthermocouple were placed 100 grams of diethylene trinitramine, 25.2grams of paraformaldehyde and 1.5 L anhydrous dioxane. Dry HCl gas wasadded just under the reaction surface while keeping the temperaturebelow 25° C. The reaction was initially very exothermic. HCl gas wasadded for 4 to 5 hours until the solution was almost clear. The solutionwas stirred overnight at 15° C., then HCl gas was added for 5 min untilthe solution was again clear. The solvent was evaporated in air and thepasty solid was dissolved by boiling in 1 L of chloroform. Thechloroform solution was stirred over sodium sulfate to remove aninsoluble yellow oil. The solvent was removed by rotary evaporation toyield 83 grams of pinkish-orange oil. The crude product was crystallizedfrom chloroform.

[0074] Step 3. Preparation of1,9-bis-(3′,5′-dinitro-1′,2′,4′-triazolo)-2,5,8-trinitrazanonane

[0075] In a 1 L round bottom flask at room temperature, 400 ml ofacetonitrile were added, then 9.2 grams of1,9-dichloro-2,5,8-trinitrazanonane were added. The slurry was stirredat ambient temperature until all of the solid had dissolved. To thissolution were added 10.82 grams of potassium dinitrotriazole and 5.65grams of sodium bromide. The reaction was stirred overnight at ambienttemperature. The solvent was removed by rotary evaporation to yield 16.6grams of a mixture that contained the crude product. The solid wassuspended in water and extracted with ethyl acetate, washed with sodiumbicarbonate and dried over magnesium sulfate. Evaporation of the solventyielded 14.1 grams of clean product in the form of a clathrate.

Example 3 Preparation of1,6-bis-(3′,5′-dinitro-1′,2′,4′-triazolo)-2,5-dinitrizahexane (BNDNH)

[0076] Step 1. Preparation of ethylene dinitramine

[0077] In a 500 ml 3-neck round bottom flask equipped with athermometer, magnetic stir bar and Argon inlet was placed 168 ml of 98%nitric acid, which was cooled to 0° C. To the acid was then added 83.6grams of ethylene urea, portion-wise, while keeping the temperaturebelow 20° C. The reaction was then stirred under these conditions for 1hour and subsequently allowed to warm to room temperature. The reactionwas quenched in ice water and the precipitate that formed was collectedby filtration. This product was added into approximately 1 L of boilingwater in small portions. The temperature was maintained until no moregas was seen to evolve. The aqueous solution was cooled in an ice bathand the ethylene dinitramine product was collected by filtration. Thereaction yield was 68% of theoretical of the dried product.

[0078] Step 2. Preparation 1,6-dichloro-2,5-dinitrazahexane

[0079] In a 5 L jacketed 3-neck reactor equipped with a top stirrer andthermocouple were placed 100 grams of ethylene dinitramine, 40 grams ofparaformaldehyde and 1.5 L of dioxane. HCl gas was added to the reactionwhile keeping the temperature below 25° C. The reaction was initiallyvery exothermic. The addition was continued for several hours until theproduct was consumed, as shown by NMR. The solvent was removed by rotaryevaporation to yield a heavy oil. The crude1,6-dichloro-2,5-dinitrazahexane product was dissolved in 300 ml ofchloroform and cooled in an ice bath. The solid was collected byfiltration and washed with chloroform. The product was air driedovernight. The reaction yield was 63.5%.

[0080] Step 3. Preparation of1,6-bis-(3′,5′-dinitro-1′,2′,4′-triazolo)-2,5-dinitrazahexane

[0081] In a 500 ml round bottom flask at room temperature, 250 ml ofacetonitrile and 3.4 grams of 1,6-dichloro-2,5-dinitrazahexane wereadded and stirred until all solid was dissolved. To this solution wereadded 5.5 grams of potassium dinitrotriazole and 3.1 grams of sodiumbromide. The reaction was stirred for 2 days until the starting materialwas consumed, as shown by NMR. The solvent was removed by evaporation.The solid was dissolved in water, extracted with ethyl acetate, washedwith brine, then dried over magnesium sulfate. The reaction yielded 3.2grams of crude product in the form of a clathrate.

Example 4 Preparation of1,5-bis(3,5-dinitro-1,2,4-triazolo)-2,4-nitrazapentane

[0082] Step 1. Preparation of methylene bis(formamide)

[0083] 50 grams (0.357 mol) of tetramine and an excess of formamide wereheated to 140° C. for 5 hours. The reaction mixture was cooled,filtered, and washed with clean formamide. The solid was recrystallizedfrom boiling ethanol to yield 16 grams (43%) of methylene bis(formamide)product. The liquor from the reaction mixture may be recycled insubsequent reactions (50.0 grams of tetramine, same reaction conditions)to afford greater yields of methylene bis(formamide).

[0084] Step 2. Preparation of methylene bis(nitramine)

[0085] 50.0 grams (0.490 mol) of methylene bis(formamide) was slurriedin 186 ml of acetic anhydride while stirring at 5° C. 186 ml of nitricacid (96%) were added over a 1.5 hour period to the slurry, maintainingthe reaction temperature between 5° C. to 10° C. during the addition.The reaction was stirred for 3 hours at the same temperature followingcomplete addition of the nitric acid, and then was poured over an icewater bath (approximately 1 L). The precipitate was filtered off, washedwith three 300 ml portions of cold (5° C.) water, and washed with three300 ml portions of 2.0 N HCl. The solid was placed in a loosely coveredbeaker and allowed to stand overnight at room temperature. The carbonylgroups were slowly hydrolyzed off to give a solution of product informic acid, hydrochloric acid, and water. The product was crystallizedout of the solution at −30° C., filtered, and washed with a minimumamount of cold water. The product was dried under vacuum, with a yieldof approximately 41 to 43 grams (62-65%).

[0086] Step 3. Preparation of 1,5-dichloro-2,4-nitrazapentane

[0087] 88.3 grams of paraformaldehyde were suspended in 275 ml ofglacial acetic acid and HCl (gas) was bubbled through for about 2 hoursuntil the reaction solution was nearly homogeneous. A brief nitrogenpurge removed excess HCl (gas) and 80.0 grams (0.588 mol) of methylenebis(nitramine) were added to the solution. HCl (gas) addition wasresumed and continued for 1.5 hours. The methylene bis(nitramine) slowlydissolved during this time, with a slight increase in reactiontemperature noted (reaction temperature rose from 25° C. to 36° C., andslowly decreased over time). The reaction was stirred for an additional1.5 hours under nitrogen purge. The reaction was poured into 2.5 L ofice water to precipitate out the 1,5-dichloro-2,4-nitrazapentaneproduct. The product was washed with several portions of cold water toremove most of the acetic acid. Typical yields were in the 50% rangebased on the methylene bis(nitramine). The product was very sensitive toacid and decomposed (turned to a viscous oil) over time in the presenceof trace amounts of acid.

[0088] Step 4. Preparation of1,5-bis(3,5-dinitro-1,2,4-triazolo)-2,4-nitrazapentane

[0089] 25.4 grams (0.129 mol) of potassium 3,5-dinitro-1,2,4-triazole(KDNT) were slurried in 200 ml of acetonitrile/120 ml tetrahydrofuran(THF). The suspension was allowed to stir under nitrogen for 15 minutes,followed by addition of 10.0 grams (42.9 mmol) of1,5-dichloro-2,4-nitrazapentane. The reaction was allowed to stirovernight (14 hours to 16 hours) and filtered, and the filtrate wassubjected to removal of the solvents under reduced pressure. Theresulting oil was taken up in 500 ml of ethyl acetate and washedconsecutively with 100 ml saturated sodium bicarbonate solution and 100ml of water. The ethyl acetate was dried over magnesium sulfate andfiltered, and the solvent removed under reduced pressure.

Example 5 Purification of1,5-bis(3,5-dinitro-1,2,4-triazolo)-2,4-nitrazapentane

[0090] The 1,5-bis(3,5-dinitro-1,2,4-triazolo)-2,4-nitrazapentane wasprecipitated from tetrahydrofuran/dichloromethane and dried severalhours under vacuum. A sample of about 5 grams was added to boilingmethanol (500 ml) and stirred vigorously for about ½ hour until no moresolid dissolved. The warm methanol was filtered to remove anyundissolved solid (crude BNDP). The methanol was allowed to cool to roomtemperature, then cooled in an ice bath. Cold dichloromethane was addedslowly to the cold methanol solution until a solid precipitated out. Thesolution was filtered, and the collected solid (BNDP) was washed with asmall amount of cold methanol. The purified material was dried undervacuum for several hours.

Example 6 Purification of1,7-bis-(3′,5′-dinitro-1′,2′,4′-triazolo)-2,4,6-trinitrazaheptane (BNTH)

[0091] In 5 ml test tubes, 250mg of BNTH were dissolved in 2 ml ofvarious hot solvents. The homogeneous solutions were then added tovarious nonsolvents until the solution was turbid. The solvent mixtureswere then cooled in an ice bath for 30 minutes, then examined forcrystal growth. The combinations of solvents and nonsolvents examinedare shown below. The combination of THF and MTBE yielded crystals buttraces of THF were never completely removed from samples. Methanol andmethylene chloride was marginally successful, yielding very smallcrystals; however, large amounts of methanol were used due to the lowsolubility of BNTH in methanol. Solvents Nonsolvents Nitrobenzene MTBENitrobenzene Ethanol Nitrobenzene Isopropanol Nitrobenzene WaterNitromethane MTBE Nitromethane Ethanol Nitromethane IsopropanolNitromethane Water Acetonitrile Xylene Acetonitrile Water AcetonitrileChlorobenzene Acetonitrile Toluene *Methanol Methylene chloride THF MTBE

[0092] The effective yields were generally 20 to 50 weight percent, withthe exception of methanol/methylene chloride, which was found to provideeffective yields of up to 75 weight percent.

Example 7 Preparation of Potassium 3,5-dinitro-1,2,4-triazole (KDNT)

[0093] Step 1. 3,5-diamino-1,2,4-triazole (DAT)

[0094] 20.0 grams (0.238 mol) of dicyandiamide were suspended in 50 mlof water and stirred vigorously. Hydrazine sulfate (15.5 grams, 0.119mol) was added, and the mixture was heated. When the temperature of themixture reached 50° C., hydrazine hydrate (5.8 ml, 0.119 mol) was added,and the reaction was heated to 120° C. to 125° C. All of the solidsslowly dissolved, and the reaction was allowed to stir at thistemperature for 16 hours. After this time, a small amount of solid hadformed in the reaction. Heating was discontinued and the reactionmixture was cooled to room temperature. The reaction was filtered andthe precipitate was washed with 20 ml of cold (5° C.) water. Thefiltrate was concentrated on a rotary evaporator to near dryness. Theresultant solid was washed with four 50 ml portions of 25%ethanol/tetrahydrofuran and dried under vacuum. The product yield of55.4 grams indicates contamination with the side-product (ammoniumsulfate). The isolated product was approximately 70-75% DAT.

[0095] Step 2. Potassium 3,5-dinitro-1,2,4-triazole (KDNT)

[0096] 27.0 grams (˜0.20 mol) of crude DAT (from the above procedure)was dissolved in 1.01 liters of 1.0 N HCl. A one-liter, three-neck roundbottom flask was fitted with a nitrogen inlet adapter, overhead stirrer,and addition funnel. The flask was charged with 125.4 g (1.82 mol) ofsodium nitrite and 150 ml of water and cooled to 4° C. The DAT/HClsolution was added dropwise over a 3.5 hour period (maintaining thereaction temperature at 4° C.). After complete addition of the DATsolution, the reaction was heated to 60° C. for 1.5 hours and cooledback down to 4° C. and 135 ml of 6.0 N HCl were added. The reaction wasallowed to warm to room temperature and stir for 16 hours. The reactionwas extracted with seven 100 ml portions of methyl tert-butyl ether(MTBE). The MTBE was stripped on a rotary evaporator until near dryness.The viscous, orange oil which remained (32.6 grams of crude3,5-dinitro-1,2,4-triazole) was dissolved in 550 ml of acetone. 20.2grams (0.20 mol) of potassium bicarbonate was added slowly to theacetone/DNT solution (vigorous bubbling ensued). This reaction mixturewas filtered, and the acetone was removed under reduced pressure. Thecrude KDNT was dissolved in 150 ml of water. Some insoluble matter wasfiltered off, and the aqueous KDNT solution was concentrated to neardryness on a rotary evaporator. The solid residue was dissolved inminimum amount of water, to which cold isopropyl alcohol was added untila yellow-orange precipitate was observed. The KDNT was filtered andwashed with cold isopropyl alcohol. Yield of KDNT was 20.3 grams (51%).

[0097] The foregoing detailed description of the preferred embodimentsof the invention has been provided for the purpose of explaining theprinciples of the invention and its practical application, therebyenabling others skilled in the art to understand the invention forvarious embodiments and with various modifications as are suited to theparticular use contemplated. This description is not intended to beexhaustive or to limit the invention to the precise embodimentsdisclosed. Modifications and equivalents will be apparent topractitioners skilled in this art and are encompassed within the spiritand scope of the appended claims.

What is claimed is:
 1. A method for preparing an energetic material, themethod comprising: heterocyclomethylating a polynitrazaalkane having atleast one terminal nitraza moiety in at least one solvent to form aclathrate comprising an N-heterocyclomethyl polynitrazaalkane; andrecovering the N-heterocyclomethyl polynitrazaalkane from the clathrateby precipitation in a non-solvent.
 2. The method of claim 1, whereinheterocyclomethylating a polynitrazaalkane having at least one terminalnitraza moiety in at least one solvent to form a clathrate comprising anN-heterocyclomethyl polynitrazaalkane comprises halomethylating thepolynitrazaalkane with a halogenating agent to form an N-halomethylpolynitrazaalkane, the N-halomethyl polynitrazaalkane comprising anN-halomethyl moiety having a halogen atom, the halogen atom comprising amember selected from the group consisting of chlorine, bromine, andiodine.
 3. The method of claim 2, wherein heterocyclomethylating apolynitrazaalkane having at least one terminal nitraza moiety in atleast one solvent to form a clathrate comprising an N-heterocyclomethylpolynitrazaalkane comprises substituting a heterocyclic nucleophile forthe halogen atom of the N-halomethyl polynitrazaalkane to form theN-heterocyclomethyl polynitrazaalkane, said substituting taking place inthe solvent.
 4. The method of claim 3, wherein substituting aheterocyclic nucleophile for the halogen atom of the N-halomethylpolynitrazaalkane comprises substituting a triazole for the halogenatom.
 5. The method of claim 3, wherein substituting a heterocyclicnucleophile for the halogen atom of the N-halomethyl polynitrazaalkanecomprises substituting a triazole having at least one nitro substituentfor the halogen atom.
 6. The method of claim 3, wherein substituting aheterocyclic nucleophile for the halogen atom of the N-halomethylpolynitrazaalkane comprises substituting a triazole having two nitrosubstituents for the halogen atom.
 7. The method of claim 3, whereinsubstituting a heterocyclic nucleophile for the halogen atom of theN-halomethyl polynitrazaalkane comprises substituting imidazole for thehalogen atom.
 8. The method of claim 3, wherein substituting aheterocyclic nucleophile for the halogen atom of the N-halomethylpolynitrazaalkane comprises substituting at least one member selectedfrom the group consisting of mononitroimidazole, dinitroimidazole, andtrinitroimidazole for the halogen atom.
 9. The method of claim 1,wherein forming a clathrate comprising an N-heterocyclomethylpolynitrazaalkane comprises forming a clathrate comprising at least onepair of methylene-spaced nitramine moieties.
 10. The method of claim 1,wherein forming a clathrate comprising an N-heterocyclomethylpolynitrazaalkane comprises forming a clathrate comprising at least twopairs of methylene-spaced nitramine moieties.
 11. The method of claim 1,wherein forming a clathrate comprising an N-heterocyclomethylpolynitrazaalkane comprises forming a clathrate comprising twoheterocyclomethyl groups.
 12. The method of claim 1, wherein forming aclathrate comprising an N-heterocyclomethyl polynitrazaalkane comprisesforming a clathrate comprising1,5-bis-(3′,5′-dinitro-1′,2′,4′-triazolo)-2,4-dinitrazapentane.
 13. Themethod of claim 1, wherein forming a clathrate comprising anN-heterocyclomethyl polynitrazaalkane comprises forming a clathratecomprising1,7-bis-(3′,5′-dinitro-1′,2′,4′-triazaol)-2,4,6-trinitrazaheptane. 14.The method of claim 1, further comprising selecting the non-solvent tocomprise a member selected from the group consisting of methanol andmethylene chloride.
 15. The method of claim 1, whereinheterocyclomethylating a polynitrazaalkane having at least one terminalnitraza moiety in at least one solvent to form a clathrate comprising anN-heterocyclomethyl polynitrazaalkane comprises: hydroxymethylating theterminal nitraza moiety of the polynitrazaalkane to form at least oneN-hydroxymethyl nitraza moiety; esterifying the N-hydroxymethyl nitrazamoiety of the polynitrazaalkane with a leaving group; and substitutingthe heterocyclic nucleophile for the leaving group of thepolynitrazaalkane to form an N-heterocyclomethyl polynitrazaalkane, saidsubstituting taking place in the solvent.
 16. The method of claim 1,further comprising preparing the polynitrazaalkane by a methodcomprising: providing a polyamine comprising at least one primary aminemoiety and at least one secondary amine moiety; perchlorinating thepolyamine to convert the at least one primary amine moiety into aN-perchlorinated amine moiety having two chlorine atoms and to convertthe at least one secondary amine moiety into an N-chlorinated aminemoiety having one chlorine atom; nitrating the polyamine to substituterespective nitro moieties for one of the chlorine atoms of theN-perchlorinated amine moiety and for the chlorine atom of theN-chlorinated amine moiety; and dechlorinating the polyamine.
 17. Themethod of claim 1, further comprising preparing the polynitrazaalkane bya method comprising: providing a polyamine comprising at least twoprimary amine moieties; perchlorinating the polyamine to convert the atleast two primary amine moieties into respective N-perchlorinated aminemoieties each having two respective chlorine atoms; nitrating thepolyamine to substitute respective nitro moieties for one of thechlorine atoms of each of the N-perchlorinated amine moieties; anddechlorinating the polyamine.
 18. The method of claim 1, furthercomprising preparing the polynitrazaalkane by a method comprising:providing a polyamine comprising at least one primary amine moiety andat least one secondary amine moiety; acylating the polyamine to convertthe at least one primary amine moiety into an acylated amine moietywhile leaving the at least one secondary amine moiety non-acylated;nitrating the N-acylated polyamine to substitute respective nitromoieties for hydrogen atoms of the acylated amine moiety and thenon-acylated secondary amine moiety; and deacylating the acylated aminemoiety.
 19. The method of claim 1, further comprising preparing thepolynitrazaalkane by a method comprising: providing a polyaminecomprising at least two primary amine moieties; acylating the polyamineto convert the at least two primary amine moieties into respectiveacylated secondary amine moieties of an N-acylated polyamine; nitratingthe N-acylated polyamine to substitute respective nitro moieties forhydrogen atoms of the acylated amine moieties; and deacylating theacylated amine moieties.
 20. The method of claim 1, whereinheterocyclomethylating a polynitrazaalkane having at least one terminalnitraza moiety in at least one solvent to form a clathrate comprising anN-heterocyclomethyl polynitrazaalkane comprises heterocyclomethylating1,2-dinitrazaethylene.
 21. The method of claim 1, further comprisingpreparing the polynitrazaalkane from imidazalidinone.